Automated micro Loop Flow Reactor technology to measure nutrients in coastal water: State of the art and field application

Abstract

Nutrient pollution is one of worldwide most diffused, expensive and challenging environmental issues.The monitoring of nutrients in coastal areas is a complex task, due to the fact that the available methods reaching the required sensitivity are based on optical wet chemistry measurements. In order to be representative, a reliable water sample collection for further laboratory analysis requires a very strict protocol and sample handling. Because of this, most of the scientists agree in affirming that the best and practical solution is to measure nutrients directly on field. SYSTEA S.p.A. has been working in the last two decades to improve automated solutions for on-line nutrient monitoring. The micro Loop Flow Reactor (μLFR) technology was presented in 2009 in Oceans conference in Biloxi (USA) and is currently a consolidated technique allowing the field measurement of nutrients in different environmental conditions.Fast growing urbanization and industrialization of river basins and coastal areas in China are imposing the local Government to improve large water quality monitoring networks; during the last few years, around one hundred in-situ nutrient multi-parameter probes (NPA pro and WIZ) were installed and provided extensive long term data to support the environmental control and related decisions making policy.The WIZ probe is an advanced real time instrument to measure the nutrient concentrations in aquatic environments. In particular, it is the only portable and submersible equipment able to measure the total concentrations of both phosphorus and nitrogen. The uniqueness of this probe is given by the fact that the unit performing the sample digestion, required for the analysis of both total phosphorus and nitrogen, was downscaled to fit within the probe.The efficiency of NPA pro and WIZ probes in measuring the concentrations of ammonia, nitrate, phosphate and nitrite was evaluated on field deployments in coastal waters, in China and South Korea, respectively. Importantly, the probe results were found to be highly correlated with laboratory measurements.The μLFR technology was also applied to the design and manufacturing of μLFA modules, on-line nutrient analyzers integrated in Ferrybox systems for the measurement of ammonia and orthophosphates. In situ results obtained in Ferrybox installations were compared and correlated with laboratory analysis of grab samples.Finally, a number of practical solutions for the improvement of NPA pro and WIZ probes in terms of instrument robustness, data reproducibility, deployment life and reliability, were, for the first time, presented and discussed.The Alliance for Coastal Technologies (ACT) is a US partnership of research organizations, water stakeholders and private companies competent in the field of nutrient management which, by means of dedicated market surveys, were able to catalogue the most frequently requested specifications for nutrient analyzers. This record was used as a guide to assess the current performance level of μLFR-based probes and modules with resp...

Path to Impact for Autonomous Field Deployable Chemical Sensors: A Case Study of in Situ Nitrite Sensors

“…103 The Systea probes have autonomously collected and reported measurements of nitrite, nitrate, orthophosphate, and ammonia in an unmanned time series monitoring station, 104,105 at 1500 m depth, 51 tethered to a solar and wind energypowered platform, 106 and in automated sensor networks spanning multiple years of operation in open natural waters. 103,107 Reports documenting in-field use and instrument intercomparsions suggest the probes have been able to discriminate between low levels of nitrite (subμg/L) in oligotrophic waters and withstand exposure in coastal waters for weeks at a time. 51,103,107,108 One of SubChemSystems' (USA) current FDS, the Autonomous Profiling Nutrient Analyzer (APNA), is designed to measure submeter scale nutrient gradients in either autonomous interval or continuous data collection mode.…”

“…103,107 Reports documenting in-field use and instrument intercomparsions suggest the probes have been able to discriminate between low levels of nitrite (subμg/L) in oligotrophic waters and withstand exposure in coastal waters for weeks at a time. 51,103,107,108 One of SubChemSystems' (USA) current FDS, the Autonomous Profiling Nutrient Analyzer (APNA), is designed to measure submeter scale nutrient gradients in either autonomous interval or continuous data collection mode. 98 SubChemSystems' instrumentation has been reported to track nitrite and other nutrients in chemical plumes, 109 investigate thin plankton layers and the influence of stratification and turbulence, identify fine-scale structures of nitrite profiles, and investigate biogeochemical cycling at ecologically critical scales for model validation and support.…”

Industry Partnership: Lab on Chip Chemical Sensor Technology for Ocean Observing

“…Because of the superior metrology performance of reagent based analytical methods (Waterbury et al, 1996;Patey et al, 2008Patey et al, , 2010Ma et al, 2014a;Nagul et al, 2015;Birchill et al, 2019;Takeshita et al, 2020), numerous sensors and analytical systems have been developed employing these techniques. This includes in situ deployed systems for Nitrate (Jannasch et al, 1994;David et al, 1998;Steimle et al, 2002;Adornato et al, 2007;Vuillemin et al, 2009;Yaqoob et al, 2012;Bodini et al, 2015), Phosphate (Adornato et al, 2007;Barnard et al, 2009;Moscetta et al, 2009;Ma et al, 2014b;Bodini et al, 2015;Yang et al, 2020), Iron (Chapin et al, 2002;Johnson et al, 2007;Huang et al, 2012;Meyer et al, 2012), and pH (Waterbury et al, 1996;Bellerby et al, 2002;Martz et al, 2003;Liu et al, 2006;Nakano et al, 2006;Wang et al, 2007Wang et al, , 2015Seidel et al, 2008;Assmann et al, 2011;Spaulding et al, 2011;Lai et al, 2018). Some of these systems are commercially available (Hanson, 2000;Barnard et al, 2009;Spaulding et al, 2011;Bodini et al, 2015;…”

“…This includes in situ deployed systems for Nitrate (Jannasch et al, 1994;David et al, 1998;Steimle et al, 2002;Adornato et al, 2007;Vuillemin et al, 2009;Yaqoob et al, 2012;Bodini et al, 2015), Phosphate (Adornato et al, 2007;Barnard et al, 2009;Moscetta et al, 2009;Ma et al, 2014b;Bodini et al, 2015;Yang et al, 2020), Iron (Chapin et al, 2002;Johnson et al, 2007;Huang et al, 2012;Meyer et al, 2012), and pH (Waterbury et al, 1996;Bellerby et al, 2002;Martz et al, 2003;Liu et al, 2006;Nakano et al, 2006;Wang et al, 2007Wang et al, , 2015Seidel et al, 2008;Assmann et al, 2011;Spaulding et al, 2011;Lai et al, 2018). Some of these systems are commercially available (Hanson, 2000;Barnard et al, 2009;Spaulding et al, 2011;Bodini et al, 2015;Lai et al, 2018). However, previously there has not been widespread uptake of these technologies for operational oceanography because of perceived and actual barriers presented by: reliability (many moving parts); fragility; complexity of operation (such as reagent preparation and pre/post deployment protocols); device size, weight and power; and significant volumes of reagent consumption and waste production.…”

Design, development and performance evaluation of ultra low-power wireless sensor network devices

“…LoRa interface as the low-rate link and an LTE one for high-throughput demanding applications. Moreover, the device interfaces with the WIZ probe [29], which is an in-situ nutrient probe. Also, it features several power mosfets to control the power of the WIZ probe and it's filtration system (pumps).…”